MgSo(4) was added to 3 com. fertilizers based on NH4NO3 and contg. various am. of dolomite or anhydrite to study mech. strength and durability of granules after 1-18 months long storage. In addn., the total N content in aq. soil filtrates, previously sep. doped with each type of corn. and tested fertilizers was detd. in pot expts. to est. their soly. The enrichment of fertilizers in MgSO4 had a small effect on N leaching from the soil while a large negative impact on the strength and durability of fertilizer granules, esp. anhydrite-contg. granules.